Tropical Cyclones Affecting the Karratha/Dampier/Roebourne region

The Pilbara coast experiences more cyclones than any other part of Australia. Since 1910 there have been 48 cyclones that have caused damaging wind gusts in excess of 90 km/h in the Karratha, Dampier and Roebourne region. On average this equates to about one every two years. About half of these cyclones have an impact equivalent to a category one cyclone. Ten of these: 1925, 1939, 1945, 1954, Shirley 1966, Sheila-Sophie 1971, Trixie 1975, Chloe 1984, Orson 1989 and John 1999 have caused very destructive wind gusts in excess of 170 km/h*.

Along the central Pilbara coast the cyclone season runs from mid December to April peaking in February and March as shown in the graph of monthly occurrence.

The early accounts of cyclones on the central Pilbara coast focus upon the impact on the pearling fleet and to the settlements at Cossack, Wickham and Roebourne.

Since the 1960s the development of the mining and offshore oil and gas industries has increased the damage potential of cyclones. Substantial economic losses can be incurred even with the threat of a cyclone impact owing to lost production or disruptions to shipping activities. Fortunately the modern towns of Karratha and Dampier have been built according to cyclone wind ratings and are far less susceptible to damaging winds than those properties in earlier times.

Figure 1. Tropical Cyclone in the Dampier/Karratha area. Click on image to enlarge.

*Note: Wind gust speeds for events prior to 1961 have been estimated using the available mean wind speeds, mean sea level pressure, and damage reports.

Tracks

Cyclones that impact the central Pilbara coast typically form over warm ocean waters to the north of the state. Although the typical initial steering of these systems is to the southwest, those that affect the Karratha region take a more southerly or southeasterly track as they move further south as shown in figure 1. Some cyclones such as Trixie (1975), Chloe (1984) and Monty (2004), originate from near the West Kimberley and take a west to southwest track toward the Pilbara.

Flooding

By not being on a major river, Karratha and Dampier are not at risk of major flooding caused by rainfall alone. Localised flooding is certainly possible in susceptible areas along creeks and low-lying areas. Major flooding in Karratha and Dampier is typically associated with storm surge, as discussed in the next section. Flooding was a feature of historical cyclone events affecting Roebourne on the Harding River. However, the construction of the Harding River Dam, some 20 km upstream of the town, in 1983-84 has eased the flood threat to the town.

Heavy rainfall inland can cause flooding along the neighbouring major river systems such as the Fortescue, Sherlock and Maitland that can impact pastoral stations, mining activities and cause transport delays and damage to road and rail infrastructure. For example, during TC Monty in 2004 the bridge over the Maitland River was destroyed cutting road links along the North West Coastal Highway and the Harding River Dam overflowed (see photos). The flood potential of a system is not directly related to cyclone intensity but is associated with its track, speed and areal extent. Indeed rainfall totals in excess of 100 mm are common with tropical lows that move over land. In February 1997 a slow moving low moved over the west Kimberley, Pilbara and Gascoyne causing rainfall in excess of 400 mm in parts and one of the highest ever floods along the Ashburton River.

Storm Surge

Storm surge is a major threat to the Karratha region. The actual water level, called the storm tide is a combination of the storm surge and tidal variation. The worst case scenario is to have a severe cyclone pass near the town near the time of high tide, in which case the water level will be many metres above the highest astronomical tide. Given the significant tidal variations, this is a rare occurrence. Storm surge is a complex function of cyclone intensity and motion, extent of maximum winds, bathymetry and coastline shape. Even with an intense cyclone the highest surge is typically restricted to less than 80 km of the coast owing to the nature of the extent of a cyclone's maximum winds.

The graphic impact of TC Vance on the remote coast west of Onslow indicates how a storm surge can change the appearance of the coastline (see TC Vance). The early account of a cyclone in 1881 when part of the coast near Cossack had two sand ridges completely eroded away, demonstrated to the early pioneers the devastating potential of the storm surge. Fortunately there has not been a significant storm surge at Karratha or Dampier since the 1960s.

Some Notable Cyclones Impacting Karratha, Dampier and Roebourne

Tropical Cyclone

Wind Gust (km/h)

Impact Description

24-25 Dec 1870

-

A cyclone passed near Roebourne on Christmas morning, the pressure falling to 956 hpa. The cyclone caused damage to buildings and boats. Trees were so thoroughly denuded of foliage that the landscape was described as similar to that in winter in England.

6-7 Jan 1881

-

Sixteen people died as all but one large schooner either foundered or was washed ashore. Parts of the coastline were completely changed and two lines of sand hills were eroded away, indications of a significant storm surge.

7 March 1882

-

A severe cyclone passed Roebourne and Cossack in the evening causing damage to every building in the settlements. Cossack recorded a minimum pressure of 942 hPa. Despite the extensive loss of sheep from surrounding stations it was considered fortunate that only one person suffered an injury.

1 March 1889

-

Flooding was considerable at Cossack where the cyclone coincided with high tide. All crew aboard the Waratah were lost off Cape Preston and one man drowned in the river at Roebourne.

4-9 Jan. 1894

-

Within the space of five days two cyclones crossed the Pilbara coast. The first caused damage to many buildings at Roebourne and Cossack. The second cyclone caused more significant damage to the area completely washing away the previously damaged sea wall at Cossack. Over forty lives were believed to have been lost as twelve luggers and the steamer Anne were destroyed. Altogether the damage was estimated at 15000 pounds and the loss of some 15000 sheep. Flooding was also substantial.

2 April. 1898

-

A cyclone was described as causing more damage at Cossack than had ever been experienced before. Tramway, rails, road and bridges were destroyed and telegraph line downed. Houses collapsed and all boats slipped their moorings. The damage was estimated at over 30000 pounds. Whim Creek registered 747 mm of rain in 24 hours, the highest daily rainfall ever recorded in WA.

4 Jan. 1911

-

A cyclone affected the Pilbara coast between Cossack and Onslow. The Glenbank was wrecked off Legendre Island with the loss of all but one of its crew. The cyclone crossed near Mardie station where nearly every outbuilding was levelled to the ground and 6000 gallon tanks were blown away.

21-22 March 1912

-

This cyclone crossed the coast just west of Balla Balla, the port for the copper mines of the Whim Creek district, early on the 22nd. Damage extended more than 200 kilometres along the coast. A large, iron sailing ship, the Crown of England, was wrecked on Depuch Island; a similar vessel, the Concordia, was driven ashore nearby. Several lighter vessels and pearling luggers were sunk or wrecked. The Koombana was lost at sea off Port Hedland with none of the 140 people aboard surviving. In total the cyclone claimed well over 150 lives.

21 Jan.1925

102 est.

Only a very small portion of the land end of the Point Samson jetty was left intact. Almost 5 km of the tramline was washed away and the Pope's Nose Creek bridge was badly damaged.

At Cossack the sea in the creek rose 7.2 m, covering the road and surrounding country for about a mile (1.6 km). Seven luggers and a schooner which had sheltered in Cossack Creek were lifted 100 m into the mangroves by the storm surge.

Not a building was left unscathed in Roebourne. Residents sheltered in more substantial stone buildings as the timber houses were razed. The Jubilee Hotel was unroofed and the other two hotels badly damaged.

11 Jan. 1939

>117

Nine people died with the loss of the Nicol Bay, on a holiday cruise to the Ashburton River. Some Roebourne properties sustained damage.

6 Mar 1945

>117

Severe damage was done to Roebourne and Point Samson. The Harding River broke its banks and flooded back yards.

31 Dec. 1954

.

Every building was damaged in Roebourne. The Point Samson jetty was wrecked and a locomotive shed and workshop demolished. Damage was conservatively estimated at 50,000 pounds. The eye passed over Lewis Island driving ashore the Dulverton then moved over Roebourne from 3:20 to 4:30 pm. Damage was extensive at Coolwanyah and Pyramid stations.

1 March 1956

-

A cyclone moved parallel to the Pilbara coast before heading down the west coast. The Point Samson jetty was washed away and many telegraph lines from Roebourne to Onslow were blown down. The Harding River flooded into Roebourne.

Shirley 2 Apr 1966,

204

Shirley passed crossed the coast at King Bay where a ship recorded winds to 204 km/h. In Roebourne, winds destroyed some buildings. Sherlock station recorded 404 mm and subsequent floodwaters damaged the Mount Goldsworthy and Hamersley iron-ore railways under construction, roads and other facilities along the Northwest coast. However, considering the intensity, the cyclone caused only minor damage.

Kerry, 21 Jan 1973

140 Cape Lambert

At Wickham more than 30 houses were partly unroofed and some houses received major damage. There was no damage to buildings in Dampier, Roebourne or Karratha as the cyclone crossed the coast well to the east. Kerry passed close to a number of oil-drilling rigs causing damage and lost productivity time that cost over one million dollars.

Trixie, 19 Feb 1975

259 (Mardie)

Trixie moved along the central Pilbara coast affecting many communities from Roebourne to Onslow, where the worst damage occurred. Property damage at Dampier was estimated at $900,000. Three blocks of flats were unroofed, as were two blocks of single men's quarters. A concrete block garage collapsed when a service station roof landed on it. Windows were blown in. At the Cape Lambert facility, doors and roofs were damaged at the workshop and warehouse. The Ore Processing plant lost cladding from sheds and a transportable electrical workshop disintegrated. Point Samson, Roebourne and Wickham all sustained major property damage.

Chloe, 29 Feb. 1984

193

Chloe crossed the coast near Roebourne where three houses were destroyed and twelve others unroofed. Fifty people required evacuation as floodwaters from the Harding River rose to the lower steps of the Police Station. Parts of the Wickham High School were severely damaged and two buildings and a boat were destroyed in the Cossack/Point Samson area. The Dampier Yacht Club was unroofed.

Orson crossed the coast near Cape Preston, 56 km west of Dampier having an estimated pressure of 920 hPa. Orson caused a storm surge of 3.1 m at Dampier but fortunately it crossed near the time of low tide. Wave action did cause significant erosion of sea walls at Dampier Port. Although weakening, Orson caused widespread structural damage at Pannawonica. The total damage cost was estimated to be in excess of $20 million in addition to the substantial cost to offshore oil and gas infrastructure. Several Indonesian fishing vessels were reported sunk near Ashmore Island with at least four lives lost.

John, 15 Dec. 1999

210 Cape Lambert

John crossed the coast to the east of Roebourne in the vicinity of Whim Creek where the hotel was extensively damaged. Cape Lambert averaged 150 km/h winds for five hours, but fortunately damage was of a minor nature in Karratha, Dampier and Roebourne. Rainfall exceeded 300 mm along a strip on its track from Sherlock station to Wittenoom.

Monty passed over Mardie station to the west of Dampier after passing near Barrow and Varanus Islands. Although little wind damage was recorded, widespread rainfall caused significant flooding. Two people were rescued from the roof of the Yarraloola homestead on the Robe River and the town of Pannawonica was cut-off. The bridge over the Maitland River on the Northwest coastal highway was destroyed. Monty also caused substantial economic losses to the offshore oil and gas industry.

Clare crossed the Pilbara coast between Dampier and Mardie after midnight early on Monday 9 January. Dampier experienced very destructive winds for a period Monday evening as the eye wall passed over the town. Karratha narrowly escaped the eye wall but still experienced destructive winds (category 2 intensity) for over seven hours and gale force winds for sixteen hours.

Glenda was a small and intense system that developed very rapidly after moving off the northwest Kimberley coast. Glenda reached category 5 intensity but weakened as it approached the Pilbara coast. Although threatening to cross the coast near the populated Dampier/Karratha region as a Category 4 system close to the time of high tide, Glenda took a more SW course towards Onslow and weakened before finally crossing the coast near Onslow at 10pm on 30 March as a marginal category 3 system. Very destructive winds were recorded on the coast at Mardie prior to crossing